The advent of rotary engines was intended to supplant reciprocating engines, thereby to reduce energy losses caused by the reciprocation of pistons, to reduce the number of moving parts, and also, friction losses. In this way it was intended to increase the number of revolutions per minute, and also to increase engine efficiency.
Rotary engines may include a pair of rotors arranged for rotation within a sealed engine cavity. The rotors are connected to an output shaft or driver. A combustible fuel mixture is provided to the engine cavity and ignited. An increase in pressure in the engine cavity due to ignition of the fuel-air mixture results in a driving force being applied to the rotors, thereby causing rotation of the driver.
There are also known rotary pumps and motors which have certain similarities to the above-described engine. An indication of the state of the art may be obtained by referring to the following patent publications:
U.S. Pat. No. 3,078,807, entitled Dual-Action Displacement Pump; PA1 French Patent No. 9204757, publication no. 2,690,201; PA1 U.S. Pat. No. 3,726,617, entitled Pump or a Motor Employing a Couple of Rotors in the Shape of Cylinders with an Approximately Cyclic Section; and PA1 U.S. Pat. No. 5,152,683, entitled Double Rotary Piston Positive Displacement Pump with Variable Offset Transmission Means.
The above patents generally do not provide structures which are conducive for use as internal combustion engines.
In the field of internal combustion engines, it is desirable to sustain high operating temperatures, thereby to maximize engine efficiency, in accordance with the well known Carnot Law.
In the field of rotary internal combustion engines, there are known the following publications: U.S. Pat. No. 2,845,909, entitled Rotary Piston Engine, to Pitkanen; and U.S. Pat. No. 4,666,383, entitled Rotary Machine, to Mendler.
Pitkanen teaches a rotary piston engine having a pair of cam-shaped rotors which are arranged for parallel rotation inside an engine casing. Pitkanen is unable to work at high speeds due to the shape of the rotors, and, furthermore, seeks to cool the engine, thereby preventing an increase in temperature which, in Pitkanen's engine, is undesired. This results in an inefficient engine, based on the well known Carnot Law, in which efficiency is proportional to the temperature difference between the interior and exterior of the engine, which Pitkanen does not sustain.
Mendler teaches a rotary piston engine having a pair of cam-shaped rotors which are arranged for parallel rotation inside an engine casing. Each rotor is described in the cited patent (column 8, lines 1-6) as having "major and minor cylindrical surfaces . . . , each centered on the axis A of the rotor, and diametrically opposed, . . . joined by cylindrical transition surfaces . . . " Furthermore, a plurality of seals are provided, thereby to provide rotor-to rotor and rotor-to-bore-wall seals (column 7, lines 62-64). It will be appreciated that, due to the presence of seals, the engine taught by Mendler is not only unable to sustain high rotational speeds, due to friction losses, but also cannot operate at high temperatures, due to the necessary presence of lubricating oil in the engine cavity.